Objective operating in the infrared
Patent 7463432 Issued on December 9, 2008. Estimated Expiration Date: 
October 3, 2026. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
October 3, 2026. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 2846923 Inverse telescopic wide angle lens Night vision weapon sight Imaging optical system Patent #: 6147815 InventorsAssigneeApplicationNo. 11542815 filed on 10/03/2006US Classes:359/754Multiple component lensesExaminersPrimary: Collins, Darryl J.Attorney, Agent or FirmForeign Patent References
International ClassesG02B 27/00G06K 7/00 DescriptionRELATED APPLICATIONSThe present invention claims the benefit of the filing date of German Patent Application, Serial No. 10 2005 047 488.8, filed Oct. 4, 2005; the content of which is incorporated by reference herein. TECHNICAL FIELD The invention relates to an objective operating in the infrared, particularly for use in a night sight device. BACKGROUND OF THE INVENTION Night sight devices conventionally have an image transducer operating in the infrared, onto which an object to be observed is imaged by an objective. The objective has lenses which are transmissive in the infrared. Night sight devices often have a heavy weight and are therefore unwieldy and difficult to handle. SUMMARY OF THE INVENTION It is an object of the present invention to provide an objective for a night sight device which is distinguished by a particularly light weight and good freedom from distortion, but which is capable of fully illuminating an IR image transducer. In the objective according to the invention, an object-side or front lens group has smaller diameters then a rear or transducer-side lens group. The front lens group therefore has predominantly near-axis lens regions in which the distortions aresmall. Only in the rear lens group are lens regions having a larger distance from the objective axis also used, in order to fully illuminate the infrared image transducer. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are described in more detail hereinafter with the aid of the drawings, in which: FIG. 1 shows an axial section through a first infrared night sight device with a six-lens objective; FIG. 2 shows a similar objective as FIG. 1, but in which a rear lens of the object-side lens group of the objective is formed by two individual lenses, which bear on one another via complementary bounding surfaces; FIG. 3 shows technical data of the objective according to an exemplary embodiment of the present invention; and, FIG. 4 shows technical data of the objective according to another exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PRESENT INVENTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail one or more embodiments with the understanding that the present disclosure is to be considered as anexemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. Position specifications "front" and "rear" are used in the present description and the claims. These position specifications relate to an observer of the night sight device, who looks from the object side onto the objective and at the transducerlying behind the objective. The adjective "object-side" is sometimes used instead of "front" and the adjective "transducer-side" instead of "rear". An objective, which comprises a housing 12 multiply stepped radially, is denoted overall by 10 in FIG. 1. The housing 12 has a multiply stepped sleeve part 14 which, on the object-side (lying on the right in FIG. 1) or front end, comprises asupport flange 16 hooking radially inwards and having an entry window 18 with a conical bounding surface. The sleeve end of the sleeve part 14 lying on the left in the drawing is provided with a screw thread. An end ring 10, which defines a likewise conical exit window 22, engages on this screw thread. The rearwardly pointing terminal surface of the support flange 16 and the forwardly pointing terminal surface of the end ring 20 form positioning shoulders, between which two lens groups G1 and G2 are held axially in series without play. The lens group G1 comprises a front lens L1, which is biconvex and made of ZnBaF6. A second or rear lens L2 of the front lens group G1 is provided behind the lens L1, while being separated by a spacer ring D1. It is a convex/concave lens which is produced from ZnF7. Between the front lens group G1 and the rear lens group G2, there is a spacer ring D2 which separates the two lens groups considerably. Its axial dimension amounts to approximately one third of its outer radius. The second lens group G2 comprises a front lens L3, which is designed as a concave/convex lens. This lens is produced from ZnF7, and the radius of its front bounding surface is significantly greater than that of its only weakly curved rearbounding surface. The rear bounding surface of the lens L3 is complementary to the front bounding surface of a further lens L4, which lies without separation on the rear side of the lens L3. The lens L4 is produced from ZnBaF6. Its rearward curvature issignificantly greater than its front curvature. Slightly separated from the lens L4 by a further spacer ring D3, there is a fifth lens L5 of the objective which has a weakly concave front bounding surface and a rear bounding surface curved more strongly in relation thereto. This lens islikewise produced from ZnBaF6. A further lens L6, whose front bounding surface is weakly concave whereas its rear bounding surface is curved more strongly in relation thereto, is separated slightly from the lens L5 by a further spacer ring D4. The 6th lens is similar oridentical to the 5th lens. The radii of curvature of the concave bounding surfaces lying on the right are identical to another, and the rear bounding surfaces lying on the left in the drawing are likewise identically curved. Details regarding the radii of curvature of the various lens surfaces as well as the thickness of the various lenses, and the material from which they are made, are collated in FIG. 3. The end ring 20 of the housing 12 is provided on its outer side with a screw thread which engages in an internal screw thread of a transducer housing 24. The transducer housing 14 holds an IR image transducer 26 which is connected via leads (notshown) to an operating circuit, via which it obtains the necessary operating voltages and via which it is read out continuously in order to produce a visible image of the received infrared image on a monitor (not represented in the drawing). The exemplary embodiment according to FIG. 2 is shown on a different scale from that according to FIG. 1. The size proportions are in reality essentially similar, as shown in detail by the dimensions specified in FIG. 4. The main difference of the objective according to FIG. 2 from that according to FIG. 1 is as follows: The rear lens L2 of the object-side lens group G1 is formed by two lenses L2a and L2b, which bear on one another via complementary bounding surfaces. The lens L2a is a biconvex lens, whereas the lens L2b is a biconcave lens. The outer bounding surfaces of the lens L2, however, are again roughly concentric as in the exemplary embodiment according to FIG. 1. The sleeve part 14, the end ring 20 and the transducer housing 24 are plastic injection-moulded parts or metal parts in both exemplary embodiments. The same is true of the spacer rings D. The materials, from which the individual lenses are made,are reported in FIGS. 3 and 4. The outer side of the sleeve part 14 may carry an external screw thread 28, as schematically indicated in the figures, in order to fasten the entire unit comprising the objective and the image transducer on a portable holder. It should be emphasized that the above-described embodiments of the present invention, particularly, any "preferred" embodiments, are possible examples of implementations merely set forth for a clear understanding of the principles of theinvention. Many variations and modifications may be made to the above-described embodiments of the invention without substantially departing from the spirit and principles of the invention. All such modifications are intended to be included hereinwithin the scope of this disclosure and the present invention, and protected by the following claims. TABLE-US-00001 TABLE 1 Technical Data of the Objective according to Claim 12 (R1 = radius of the front lens surface, R2 radius of the rear lens surface) R1 R2 Thickness Diameter Lens (mm) (mm) (mm) Glass type (mm) Comment L1 29.627 15.254 2.00ZnBaF6 9.6 convex L2 7.55 6.486 2.789 ZnF7 9.6 concave L3 40.893 4.46 2.246 ZnF7 10.3 concave L4 40.27 6.607 3.00 ZnBaF6 10.3 concave L5 67.311 21.58 2.00 ZnBaF6 13.0 concave L6 67.311 21.58 2.00 ZnBaF6 14.5 concave TABLE-US-00002 TABLE 2 Technical Data of the Objective according to Claim 14 (R1 = radius of the front lens surface, R2 radius of the rear lens surface) R1 R2 Thickness Diameter Lens (mm) (mm) (mm) Glass type (mm) Comment L1 115.5 9.954 3.18LaF1 9.5 convex L2a 8.465 8.465 3.82 LaF1 9.4 convex L2b 8.465 7.383 3.22 ZnF2 9.4 concave L3 15.58 4.504 2.88 ZnF21 12.0 concave L4 15.58 7.77 3.18 ZK11 12.0 concave L5 12.742 25.30 2.73 LaF1 14.4 concave L6 223.4 33.725 2.73 BaF2 16.2 convex Field of SearchMultiple component lensesSeven components Six components First component positive + - + + - + Arrangement First two components positive + + - - + + Arrangement First component negative First two components negative Five components First component positive + - - + + Arrangement + - + - + Arrangement First two components positive + + - - + Arrangement + + - + + Arrangement First component negative Four components First component positive + - + - Arrangement + - + + Arrangement + - - + Arrangement With multiple element component Infinite radius Having a biconvex single element component + + - + Arrangement + + + - Arrangement First component negative - + + - Arrangement - + + + Arrangement Three components + - + Arrangement With multiple element first component With multiple element second component With multiple element third component With first component biconvex With third component biconvex + + - Arrangement + + + Arrangement Two components + + Arrangement + - Arrangement HAVING SIGNIFICANT INFRARED OR ULTRAVIOLET PROPERTY Having folded optical path Having polarizing element Including alternative optical path or optical element (e.g., day-night, hi-low magnification) Including continuously variable magnification or focal length (zoom lens, adjustable lens) Lens, lens system or component Infrared lens Having four or more components |
